The debate, between Vice President Kamala Harris and former President Donald Trump, will take place on Tuesday, Sept. 10 at 9 p.m. EDT.
Both had previously committed to attending.
"World News Tonight" anchor and managing editor David Muir and ABC News Live "Prime" anchor Linsey Davis will serve as moderators.
"The Race for the White House" Pre-Debate Special, anchored by Martha Raddatz, Jonathan Karl, Mary Bruce and Rachel Scott, will air at 8 p.m. EDT.
The debate is being produced in conjunction WPVI-TV/6abc, and will air on ABC and stream on 24/7 streaming network ABC News Live, Disney+ and Hulu.
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As previously announced by ABC News, to formally qualify, presidential candidates will need to hit various qualification requirements, including in polling thresholds and in appearing on enough state ballots to theoretically be able to get a majority (270) of electoral votes in the presidential election.
The National Constitution Center, which hosts exhibits and events about the U.S. Constitution and about civic engagement, is right by Philadelphia's Independence Hall, where the Declaration of Independence and the Constitution were both signed.
Debates have been held here in the past: Hillary Clinton and Barack Obama went head-to-head in the 2008 primary, and both President Joe Biden and former President Donald Trump held town halls here in 2020.
But this will be the first time Vice President Kamala Harris will be on the presidential debate stage.
"Harris is new to this. At this level, she of course debated as a vice president, but she never went head-to-head with Trump. And how Trump handles her and how she handles Trump will be a must-see TV," said ABC News political director Rick Klein.
Trump announced last week he was rejoining the ABC debate days after posting on his social media network that he would not appear on the network, citing a lawsuit he has filed.
That decision set up a highly anticipated moment in an election where the first debate led to a massive change in the race - with Democratic President Joe Biden ending his reelection bid and endorsing Harris.
Sept. 10 is the same date that Trump and Biden had agreed to their second and final debate.
Debate rules are still being worked out between the candidates. We will learn more about those in the coming weeks.